Yabby Sexing
Rob McCormack
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The Yabby is a freshwater crayfish, also known as a crawchie, crawdad, craybob or even lobbie, it's dependant on where you come from. These yabbies are also know as the western blue claw; they are a native of the Murray Darling System (west of the Great Divide) as well they are basically blue in colour. Blue claw yabbies are genetically blue, but will change colour to that which is most suitable for camouflage in the wild. Yabbies can be any colour blue, black, white, brown, red, green or any combination. Yabbies grow to a maximum size of 350 gram, however, the common large size is 120 150 gram. Yabbies have a life span of only 5 7 years under ideal conditions, in the wild their life expectancy is much shorter as then are on the bottom of the food chain and a vast amount of animals consume them. Some of their main predators are insect larvae, fish, eels, turtles, birds and water rats.
We grow all our yabbies in earthen ponds filled with rainwater. They are harvested with baited traps and the catch each day is returned to holding tanks in our purging/packaging facility. Yabbies are sorted and graded and held in tanks for at least 3 days prior to sale to ensure their waste line is clean and clear (purged).
GROWTH: Yabbies are fast growing, but to do so they must molt. Yabbies have a hard exoskeleton which limits their size, for them to grow they moult this one and grow a new one. In farm dam situations the majority of your population going from newborn to over 100mm ( 50 gram ) in one year. However, there is an extreme variation in growth rates of individuals from the same brood. Some may reach this size in six months, whereas, others may take longer than two years. Growth is dependant on the availability of food, shelter, density and water temperature. Yabbies are cold blooded animals, the warmer the water the faster their metabolism goes and the faster they grow etc. Below 10 deg.C yabbies dont feed. From 10 14 deg.C they feed but no noticeable growth, above 14 deg. C noticeable growth. Best growth when water temperatures are between 22 28 deg. C. Depending on the amount of time, effort and money available, it is possible to grow your yabbies from 0 to 150mm ( 100 gram ) plus in twelve months.
DENSITY: Yabbies survive extremely well in high density situations. Good farm dams can easily produce 1,000kgs per hectare per year and specifically designed and cared for yabby ponds may reach up to 3,000kgs per hectare per year. A density 3 - 4 yabbies per square metre is ideal with the smaller the density the faster and easier they grow. We do not recommend a density of more than 10 per square metre. A 100mm (4") yabby weighs approximately 40 - 50 grams. Yabbies are cannibalistic and death due to larger yabbies eating smaller is extremely common.
BREEDING: Yabbies are highly prolific, place a pair together and they will breed if conditions are right. Whether in a fish pond or dam with good conditions allow an average of 2 - 3 breedings per season and 1,000 young per female per year. Conditions for best breeding, long hours of light and warm water.
Yabby Sexing |
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AQUARIUMS: Aquarium yabbies make excellent pets, basically treat them the same as a gold fish. Fill the tank completely with water, yabbies breathe oxygen from the water the same as fish. An aerator or filter in the tank will keep your water fresher longer. Usually you don't have to change the water until it becomes smelly. Water quality is directly related to the amount of food placed into the water. Don't feed yabbies meat, feed your yabbies pellets or vegetables. Shelter is important, each yabby requires a home, rocks or logs in the tank are essential. See Aquarium Pets.
DAMS: Yabbies thrive in farm dams. Best dams are those without large numbers of predators in them, i.e., fish, eels, turtles, etc. Also best results will be in very turbid (Muddy ) dams, yabbies don't like clear water. Average farm dams produce 50 - 100 kgs of yabbies per year without any effort. To stock your dam use dam stock breeders 50 - 100mm head to tail, these are yabbies large enough to look after themselves, too large for most predators to eat and ready to breed. Minimum required to start a population is 100, maximum is 1,000. The more you put in the greater your chances of successfully starting a viable population. No feeding required, yabbies eat grass, leaves, seeds, whatever blows or washes into the dam plus whatever grows in the dam, weeds, algae, insects, etc. Capture via meat on a string or commercial yabby traps available from RBM Aquaculture. For further information see The Yabby Farmers Handbook.
STOCKING: Farm dams can be stocked at very low rates if Dam Stock Breeders are used. Breeders 50 100 mm head to tail are the ideal size. Larger animals over 100mm tend to wander from the dam, smaller animals are vulnerable to predation and need time before ready to breed. Dam Stock Breeders are ready to breed right away and too large for most animals to eat. Technically you only need two to start a population, one male and on female, however the chances of something happening to one is high. Plus the chance of that boy finding that girl in the dam again is astronomical. Best results are achieved by stocking with a minimum of 100 yabbies. Larger dams over 1000 square meters surface area will need 200 or more. Commercial farmers stock at a rate of one dam stock breeder per square metre. The higher the stocking the sooner a harvest.
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Cherax destructor |
AQUARIUM PETS: Yabbies make excellent Aquarium pets, but before you have one as a pet, listen to what this yabby has to say.
Hi, I'm a yabby and I want to be your pet. I'm an easy pet to look after, all I need is a home to call my own, food to eat and oxygen to breathe.
Most people keep me in a fish tank, just like a Goldfish. If I am small and the tank is large, then no aeration is required, but I would be happiest with a small aquarium aerator going all the time. Aerators are very good for me as they not only place oxygen in the water for me to breathe, but also circulate the water and reduce the risk of pollution occurring in my tank.
In my tank I also like sand or gravel on the bottom, so when I get bored I can pretend to be a bulldozer and dig holes and make mountains with the gravel. Also, a rock or log that I can climb over and make a home under would be wonderful.
As a climber none can compare, so in my tank please beware, air hoses, rocks and logs I will climb, so keep a lid on my tank all the time.
I don't eat much and most people kill my friends with kindness by over feeding them. Please don't overfeed me! I only eat a little food and if you place more than I can eat into my tank then the extra food just sits on the bottom and rots. Rotting food will pollute my water and polluted water will kill me. Please be careful I'm too young to die.
I'm not a very fussy eater. In fact I will eat almost anything if it is fresh, I don't like rotten food. Most people feed me vegetable matter, this is better than meat as meat pollutes my water very rabidly.
Specially formulated, water stabilized yabby pellets are great, also sinking fish food, budgie seed, potato peels, spinach, peas, circles of carrot and most fruits are some of my favorite foods. All aquatic plants are also excellent food, especially if you are going on holidays for a week or two. Just go down to your local creek, collect a few handfuls of water weeds and drop them into my tank. The weeds will live and grow in the tank without polluting my water, so I can eat whenever I like. If you want to feed me meat, then garden worms are best, they can live for extended periods in my tank until I get around to eating them.
I'm a prolific breeder and hundreds of young ones are the norm. If I'm a female I'll lay eggs under my tail which take 6 8 weeks to hatch into tiny baby yabbies that are miniature adults. When all my babies are running around the bottom of the tank I can be taken away from them, otherwise I may eat them. Other adults will also eat babies so if left in the tank then lots of shelter is required as the more hiding places the greater the survival.
As a baby I'm cute and friendly and I'll eat the same food as mum and dad, but I quickly become bored if fed the same food day after day, so please give me a variety.
I'm easy to look after if you follow these rules you cant go wrong, but be warned!
I'm a yabby and very strong, so be extra careful or I'll nip on!
Many people in the course of keeping yabbies for pets have the need to add extra yabbies to a tank with existing yabbies in it. This can be a problem. The ones in the tank are in their own territory, when you add extras they are invaders and a massive fight will occur with death or injury the result. To alleviate this problem, simply remove existing yabbies from the tank and rearrange it. For example move your rocks from one side to the other, mound the sand up in a corner etc. Once the tank has been rearranged, drop them all in together, old and new yabbies are all in new territory together and they will settle in harmony with little fuss.
OTHER CRAYFISH:
Cherax rotundus setosus is a common yabby from the central east of NSW. It has generated a large amount of interest in recent years as it has the ability to cross breed with both destructor and albidus generating hybrids with unique qualities. As a species it does not grow to any great size and 70 gram males would be the limit. Females are generally smaller and 40 gram would be common. It has adapted to the coastal conditions and tolerates low ph water. Generally found in semi permanent water ( shallow creek beds, swamps, stump holes and wheel tracks in wet paddocks ) and creates extensive borrows from which it can survive extended dry periods. Mainly greenish in colour with blue tints and orange joints with a rounded body, can easily be distinguished by the setae on the inside base of the claws. Generally considered a more placid, non aggressive species than destructor. Can be selectively bred for colour and fluorescent blue lines are easily generated.
Giant Spinies are a crayfish that prefers cool mountain streams and rivers. Most eastern flowing freshwater rivers in NSW have Giant Spinies in their upper reaches. Spiny crayfish made good aquarium pets, these crayfish are large, incredibly strong, dangerous to handle due to the spiny shell and exceptional escape artists. All that aside for the committed aquarium person they make a eye catching aquarium display pet. Tanks must be lidded and secured as these crayfish stand on their claws and push their tails up the side of the tank. If they can get the tip of their tail over the edge they will pull themselves out and escape.
Hairy crayfish share the same habitat as the spiny crayfish juveniles. They are a native of cool mountain streams on the eastern drainage of central eastern NSW. They are relatively small in size less than 100 mm head to tail. Similar in shape to a spiny but instead of spines have small hairs (setae ) covering their body. Greenish blue in colour with a yellow underside they are relatively shy being mostly nocturnal crayfish.
